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Design and Development of a Hybrid UAV

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Design and Development of a Hybrid UAV

  1. 1. Design and Development of a Hybrid UAV BRUNEL UNIVERSITY Design and Development of a Hybrid UAV Abbinaya T Jagannathan (1037583) Arturs Dubovojs (1008780) Bennie Mwiinga (1020511) Brett McMahon (0813201) Carlos B. Calles Marin (1018922) Camilo Vergara (1010295) Primary Supervisor: Prof. Ibrahim Esat Secondary Supervisor: Dr Mark Jabbal Word Count: 45,854
  2. 2. Design and Development of a Hybrid UAV Arthur D. i | P a g e ME5308 – Major Group Project Abstract The report of the project describes various design stages in detail as it was carried out from conceptual design stage all the way to the final aircraft testing. It describes the unique concept of fixed wing aircraft hybridised with tri-copter into a hybrid UAV. The report describes how the configuration of such aircraft was achieved through careful design stages, build and implementation, testing and further improvements and suggestions.
  3. 3. Design and Development of a Hybrid UAV Brett M. Acknowledgements The group would like to thank our supervisors and the lab technicians for their understanding, advice and assistance during the design and build of the aircraft. We owe a big thank you to lecturers Ibi Esat and Mark Jabbal for taking the time to meet with the team on a weekly basis to discuss problems and solutions during the aircraft’s design. We thank the lab technicians, in particular Kevin Robinson in the aerospace lab for his endless advice and assistance and good humour in building the aircraft. Additionally we thank the technicians Keith Withers, Steven Riley and Chris Ellis for their assistance in manufacturing and testing many of the specialised components of the aircraft, often to short deadlines. We thank Dr Alvin Gatto for his advice and expertise in preparing for and performing the flight testing of the aircraft and finally, thank you to the many external part suppliers for their effort in delivering the parts needed to build the aircraft.
  4. 4. Design and Development of a Hybrid UAV iii | P a g e ME5308 – Major Group Project Statement of Relative Contributions Every contribution to this report has been clearly marked in the header of each page with the author’s first name and initials of the surname. I confirm that all work presented is original and where other sources or reports have been referred to in the text have been referenced appropriately. Abbinaya T Jagannathan Bennie Mwiinga Carlos B Calles Marin Arturs Dubovojs Camilo Vergara Brett McMahon Shown on the table below is a personal statement of each individual’s contribution and role during the project Name Responsibilities Abbinaya T Jagannathan In the first term I started getting involved with initial geometric and performance requirements of the aircraft and later started to move into aircraft tail sizing, aircraft stability and control surface sizing. During the second term, I was involved with design and testing of components and connections required for the aircraft. I was also involved with the build manufacture of the fuselage and other aircraft components. Overall, I was working mainly on the theoretical side in the first term and more towards the practical build in the second term Arturs Dubovojs
  5. 5. Design and Development of a Hybrid UAV iv | P a g e ME5308 – Major Group Project At the beginning of the project I have extensively contributed to different aspects of the design process by selecting and analyzing key aircraft parameters and researching various topics during the preliminary design phase such as suitable motors selection and combination of aircraft stability for tri-copter and fixed wing configuration. During the detail design phase, I have designed the tail of the aircraft as well as contributed to the rod to rod connections. I further Contributed by finding suitable manufacturers of the sourced parts and handled the orders as well as other segments building and testing of the aircraft. Bennie Mwiinga In the first term I was involved in the concept and preliminary aircraft design of the aircraft. I also concentrated on the research and procurement of flight control and avionics systems that would be on the UAV so that it would to be fully functional. I was involved in initial sizing focusing on the VTOL propulsion system and what would be needed to achieve a stable VTOL UAV. In the second term I was mainly focused on the preparation and installation of avionics and the FCS onto the UAV. Additionally working on developing computer testing codes needed for component tests such as Motor Characterization. Brett McMahon
  6. 6. Design and Development of a Hybrid UAV v | P a g e ME5308 – Major Group Project During the design and build phases of the project, I assisted in creating virtual models of the aircraft and its components using 3D CAD software including Autodesk’s Inventor, AutoCAD and Dassault Systems’ Solidworks. During the second term, I assisted with hands on building. Carlos B Calles Marin During the first term I was involved in the initial sizing and development of the aerodynamics of the aircraft, mainly focusing on the wing parameters, drag estimations and performance calculations. As the project evolved I helped with the motor selection and detail design of connectors and wing. As the group leader it was also my job to manage the other team members making sure there was active communication between design phases. Camilo Vergara During early stages of the project I was involved in the initial geometric sizing of the aircraft and components through the use of Computer Aided Design (CAD) software. As the design progressed I became responsible for all aspects of the aircraft fuselage design, in addition to estimation of weight and center of gravity. Throughout the whole of term two I was heavily involved with the build of the UAV, and ultimately also helped out with the avionics towards the end.
  7. 7. Design and Development of a Hybrid UAV vi | P a g e ME5308 – Major Group Project Contents Abstract....................................................................................................................... i Acknowledgements .....................................................................................................ii Statement of Relative Contributions...........................................................................iii List of Figure .............................................................................................................. x List of Tables.............................................................................................................xv Nomenclature..........................................................................................................xvii 1. Introduction ......................................................................................................... 1 1.1. Motivation...................................................................................................... 1 1.2. Project Description........................................................................................ 3 2. Literature Review ................................................................................................ 4 2.1. State of The Art Technology.......................................................................... 4 2.2. Market Analysis............................................................................................. 9 3. Requirements.................................................................................................... 12 3.1. Regulations ................................................................................................. 12 3.2. Aims and Objectives ................................................................................... 13 Aim.................................................................................................................... 13 Objectives ......................................................................................................... 13 3.3. Mission Profile............................................................................................. 14 4. Design Process................................................................................................. 16 4.1. Concept Design........................................................................................... 16 4.1.1. Individual Proposals ............................................................................. 16 4.1.2. Quality Function Deployment................................................................ 35 4.1.3. Group Concept ..................................................................................... 37 4.2. Preliminary Design ...................................................................................... 41 4.2.1. Weights................................................................................................. 43 4.2.2. Aircraft Sizing: Constraint Analysis....................................................... 44 4.2.3. Aerodynamics....................................................................................... 48 Lift Equation.......................................................................................................... 48 Wing Geometry..................................................................................................... 48 Aerofoil Selection.................................................................................................. 52 Tail Sizing............................................................................................................. 58 The tail configuration......................................................................................... 59
  8. 8. Design and Development of a Hybrid UAV vii | P a g e ME5308 – Major Group Project Volume Coefficients: ......................................................................................... 60 Optimum tail arm and tail plan form area: ......................................................... 61 Tail Aerofoil: ...................................................................................................... 62 Drag...................................................................................................................... 63 Control Surface Sizing: Wing ............................................................................ 70 Lift Curve Slope Numerical Prediction: Wing and Aileron/Flaps........................ 73 4.2.4. Centre of Gravity .................................................................................. 78 4.2.5. Stability and Control: Standard Take-Off and Landing ......................... 81 4.2.6. Stability: Vertical Take-Off and Landing ............................................. 100 4.2.7. Structures ........................................................................................... 113 4.2.8. Computer Aided Design and Technical Drawings .............................. 131 4.2.9. Propulsion........................................................................................... 139 5. Avionics and Flight Control ............................................................................. 150 Components ....................................................................................................... 150 Main Control Scheme and sensor array ............................................................. 151 PID Controller ..................................................................................................... 153 Related software and Full system schematic...................................................... 154 Sonar and Noise Reduction................................................................................ 155 APM Anatomy..................................................................................................... 156 Manual Transition ............................................................................................... 158 6. Component Testing......................................................................................... 160 6.1. Stress Tests .............................................................................................. 160 6.1.1. Rods ................................................................................................... 160 6.1.2. Connections........................................................................................ 166 6.2. Motor Characterisation.............................................................................. 170 6.2.1. Set-Up ................................................................................................ 170 6.2.2. Calibration of Equipment .................................................................... 174 6.2.3. Procedure for Testing ......................................................................... 174 6.2.4. EDF Results ....................................................................................... 177 6.2.5. Motor Results ..................................................................................... 179 7. Build & Manufacturing Methods & Materials in Chronological Order............... 182 7.1. Logistics .................................................................................................... 182 7.1.2................................................................................................................ 183
  9. 9. Design and Development of a Hybrid UAV viii | P a g e ME5308 – Major Group Project Key materials used.......................................................................................... 184 7.2. Fuselage ................................................................................................... 187 7.3. Connections .............................................................................................. 193 7.4. Wings & Tail.............................................................................................. 194 7.5. Propulsion ................................................................................................. 195 7.5.1. VTOL Propeller motors Mount............................................................ 195 7.5.2. Lander 90 mm EDF Mount ................................................................. 197 7.6. Avionics..................................................................................................... 198 Servo Installation............................................................................................. 198 Camera, Live stream & OSD Installation......................................................... 198 GPS & Compass installation ........................................................................... 199 Sonar Installation ............................................................................................ 199 Flight Control System & Air speed sensor Installation..................................... 199 ESC Installation and calibration ...................................................................... 199 Battery and Power Distribution Harness (PDH) Installation ............................ 200 Telemetry (MAVlink) Installation...................................................................... 200 8. After Build Testing........................................................................................... 201 8.1. Flight Tests................................................................................................ 201 8.1.1. Horizontal Flight Test 1....................................................................... 201 Horizontal Flight Test 2....................................................................................... 205 8.1.2. Vertical Flight Tests ............................................................................ 208 9. V-n Diagram.................................................................................................... 210 10. Budget.......................................................................................................... 212 11. Conclusion.................................................................................................... 214 12. Improvements and Further Research........................................................... 215 Landing Gear...................................................................................................... 215 STOL Propulsion ................................................................................................ 215 Power Plant Upgrade.......................................................................................... 215 Transmitter/Camera Range ................................................................................ 216 Aircraft Systems.................................................................................................. 216 Material upgrade................................................................................................. 216 Transition attempt............................................................................................... 216 Autonomous Flight capabilities ........................................................................... 216
  10. 10. Design and Development of a Hybrid UAV ix | P a g e ME5308 – Major Group Project Tilt rotors............................................................................................................. 217 Ultimate load testing on wings and fuselage....................................................... 217 Stress testing of 3D printed parts ....................................................................... 217 13. Bibliography.................................................................................................. 218 14. Appendices................................................................................................... 228 14.1. Appendix A – Technical Details ............................................................. 228 Roskam Constraint Analysis ........................................................................... 228 Wing Profile Analysis: Additional Aerofoils...................................................... 229 Comparison between the two analysis methods in XFLR5 ............................. 230 Results for Vortex Lattice Method (VLM) and the Panel Method with a percentage comparison................................................................................... 230 Motor Test Code ............................................................................................. 235 14.2. Appendix B – Project Plan and Management ........................................ 237 14.2.1. Gantt Chart...................................................................................... 237 14.2.2. Logistics .......................................................................................... 239
  11. 11. Design and Development of a Hybrid UAV x | P a g e ME5308 – Major Group Project List of Figure Figure 1 The IAI Mini Panther in level cruise flight [1] . .............................................. 4 Figure 2 Sitter type UAV the V-Bat from MLB [4]. ...................................................... 5 Figure 3 The Orbis from Santos Labs in hover [6]...................................................... 5 Figure 4 The Latitude Engineering HQ hybrid Prototype [8]....................................... 6 Figure 5 The Wingcopter V13CH in VTOL mode. ...................................................... 7 Figure 6 Advanced VTOL Technologies' Hammerhead [10] ...................................... 7 Figure 7 Bell Eagle Eye Tiltrotor UAV [11]. ................................................................ 8 Figure 8 QTW-UAV developed by Chiba University, Japan [14]. ............................... 8 Figure 9 Graph showing basic relation between small UAVs..................................... 9 Figure 10 Maximum Endurance vs. Maximum Take-off weight for a range of UAVs [19] ........................................................................................................................... 11 Figure 11: The STOL mission profile........................................................................ 14 Figure 12: The VTOL mission profile........................................................................ 15 Figure 13 approximate sketch of the concept idea................................................... 18 Figure 14 Individual Proposal Concept by Bennie Mwiinga...................................... 21 Figure 15 The Doak VZ-4 by Doak Aircraft Company [24]. ...................................... 21 Figure 16 Blown Flight Control Concept................................................................... 23 Figure 17Tube and Tray Fuselage Concept............................................................. 25 Figure 18 Tube and Tray Fuselage as Used by Hobby Flyers ................................. 26 Figure 19 Concept Sketch of an initial idea.............................................................. 29 Figure 20 Concept Design Sketch............................................................................ 33 Figure 21 A quality function deployment (QFD) Matrix............................................. 35 Figure 22 Flow Diagram showing Design Stages..................................................... 42 Figure 23 Force Diagrams: a) Forces on a climbing aircraft, b) Forces on aircraft at constant bank angle [27]. ......................................................................................... 44 Figure 24 Constraint Analysis for the UAV............................................................... 46 Figure 25 Wing Geometry, Note: dimensions in millimetres..................................... 50 Figure 26 Induced Drag Factor Vs. Taper and Aspect Ratio [28]............................. 51 Figure 27 Typical Cambered Aerofoil [31]................................................................ 52 Figure 28 Lift Coefficient Vs. Moment Coefficient Analysis of different profiles........ 53 Figure 29 Initial and Final profile Comparison. ......................................................... 54
  12. 12. Design and Development of a Hybrid UAV xi | P a g e ME5308 – Major Group Project Figure 30 XFLR results for the final wing configuration. (a) Moment Force and chord wise lift distribution. (b) Spanwise lift distribution. (c) ISO view of lift and lift distribution................................................................................................................ 55 Figure 31 Polars: (a) Variation of Lift coefficient with AoA. (b) Variation of the drag coefficient with lift coefficient. (c) Variation of lift to drag ratio with AoA. .................. 56 Figure 32: Tail design procedure as illustrated by Mohammad Sadraey. [40].......... 59 Figure 33 Total Drag Decomposition........................................................................ 63 Figure 34 Drag velocity curve................................................................................... 66 Figure 35 CD Vs. CL Polar for the wing and the aircraft........................................... 68 Figure 36 Comparison of the Lift Curve Slopes using different predicting methods: Online database, XFLR5 and ESDU sheets............................................................. 74 Figure 37 How to obtain Trailing Edge Angle ...................................................... 76 Figure 38 Wing Curve slopes with control surface deflections. ................................ 77 Figure 39 Force balance kit to acquire aircraft CG location...................................... 79 Figure 40 Front load with dual dead weight batteries and back-up 4000 mah main battery ...................................................................................................................... 80 Figure 41: Tail incidence angle vs. Moments generated. ......................................... 82 Figure 42: Graphs indicating the derivatives and for stable and instable aircraft conditions. .................................................................................................... 84 Figure 43 Wing and tail forces.................................................................................. 86 Figure 44 Statically Stable and Unstable pitching moment curves........................... 87 Figure 45 Final aircraft CG Lift configuration............................................................ 88 Figure 46: control surface effectiveness parameter vs. control surface to lifting surface chord ratio. [40]............................................................................................ 92 Figure 47 Shows the rudder curve slope with deflection angles of ±20 degrees...... 97 Figure 48 Shows the elevator curve slope with deflection angles of ±20 degrees. .. 97 Figure 49 Longitudinal CG Envelope for Project vehicle .......................................... 98 Figure 50 Tri-copter configuration with reference axes. ......................................... 101 Figure 51 Pitch up by using Rotor 1. ...................................................................... 102 Figure 52 Roll in the Clockwise direction................................................................ 102 Figure 53 Roll in the Counter Clockwise direction.................................................. 102 Figure 54 Yaw authority of a tri-copter. .................................................................. 103 Figure 55 Mass Flow of air through rotor in hover.................................................. 104 Figure 56 Altitude Hold (Hover) with all 3 rotors..................................................... 106
  13. 13. Design and Development of a Hybrid UAV xii | P a g e ME5308 – Major Group Project Figure 57 Mass Flow of air through rotor in vertical climb. ..................................... 107 Figure 58 A level vertical climb by the tri-copter..................................................... 108 Figure 59 Flow of air through the rotor in forward flight.......................................... 109 Figure 60 Rotor Disc showing Azimuth angle......................................................... 110 Figure 61 Full model of UAV at a hover. ................................................................ 111 Figure 62 Full model of UAV in transition............................................................... 111 Figure 63 UAV model in full horizontal flight........................................................... 112 Figure 64 Monocoque fuselage design [61] ........................................................... 114 Figure 65 Truss fuselage structure [32].................................................................. 114 Figure 66 Semi-monocoque Fuselage [32] ............................................................ 115 Figure 67 Global Hawk Cutaway [64]..................................................................... 115 Figure 68 Falco Cutaway diagram [64]................................................................... 116 Figure 69 Cutaway of the ScanEagle [64].............................................................. 116 Figure 70 Bonding in progress of the Demon UAV composite structure [65] ......... 117 Figure 71 Loading on a triangular structure [68]..................................................... 118 Figure 72Skeletal frame of the fuselage................................................................. 119 Figure 73 Landing Gear Positioning for Proper Weight Distribution [71] ................ 121 Figure 74 Moveable Landing Gear Concept........................................................... 122 Figure 75 ABS Landing Gear Mount - Broken During Aircraft Assembly................ 123 Figure 76 ANSYS principle stress analysis on bulkhead displaying key on the left 124 Figure 77 demonstration of typical wing structure [75] ........................................... 127 Figure 78 Single Spar Wing Connection ................................................................ 131 Figure 79 Double Spar Wing Connection............................................................... 132 Figure 80 Moveable Landing Gear Mount.............................................................. 133 Figure 81 Computational Stress Test Result for Basic Landing Gear Mount ......... 134 Figure 82 Computational Stress Test Result for Lightweight Landing Gear Mount 134 Figure 83 Nose Vertical Lift Fan Skeletal Structure................................................ 135 Figure 84 Detail View of the Tongue and Groove Assembly Method ..................... 135 Figure 85 Initial fuselage concept........................................................................... 136 Figure 86 First Full Group CAD Aircraft Design ..................................................... 136 Figure 87 Structure and connections of various components within the aircraft..... 137 Figure 88 Top, front and side views of the final CAD model................................... 138 Figure 89 T/W vs Maximum amp draw................................................................... 140 Figure 90 T/W vs EDF price ................................................................................... 141
  14. 14. Design and Development of a Hybrid UAV xiii | P a g e ME5308 – Major Group Project Figure 91 EDF unit weight vs Thrust Capability ..................................................... 141 Figure 92 STOL mission current comparison for the initial and final endurance calculations ............................................................................................................ 148 Figure 93 VTOL mission current draw comparison for the initial and final endurance calculations. ........................................................................................................... 148 Figure 94 General control scheme of the UAV [87]................................................ 151 Figure 95 ArduPilot Mega 2.6 from 3D Robotics .................................................... 152 Figure 96 Schematic of MPU-6000. ....................................................................... 152 Figure 97 Block diagram of tri-copter control include 2 gain values [57]. ............... 153 Figure 98 Control allocation by a controller on a tri-copter..................................... 153 Figure 99 Example of Cascade Control.................................................................. 154 Figure 100 Cascaded PID used by APM [88]......................................................... 154 Figure 101 MaxBotix XL MaxSonarEZL0. .............................................................. 155 Figure 102 Sonar EM Noise reduction modification. .............................................. 156 Figure 103 APM 2.6 anatomy................................................................................. 156 Figure 104 Phases of flight during the transition maneuver from hover to horizontal flight........................................................................................................................ 158 Figure 105 Cantilever Load Testing Arrangement.................................................. 160 Figure 106 Cantilever Physical Stress Test Results Graph.................................... 161 Figure 107 Three Point Physical Stress Test Results Graph ................................. 162 Figure 108 Three Point Physical Stress Test Results Graph ................................. 163 Figure 109 demonstration of carbon fiber rod deflection with cantilever point loading ............................................................................................................................... 165 Figure 110: Experimental setup of the test conducted (left) and a drawing of the component (right) ................................................................................................... 167 Figure 111: Load vs Tensile extension for the 10mm diameter hole ...................... 168 Figure 112: Load vs Tensile extension for the 20mm diameter hole. ..................... 169 Figure 113 Thrust bench and NI High USB carrier used for motor characterisation. ............................................................................................................................... 171 Figure 114 EDF Mount for thrust bench. ................................................................ 171 Figure 115 Motor Mount for thrust bench. .............................................................. 171 Figure 116 80A ESC Turnigy Superbrain............................................................... 172 Figure 117 Turnigy KV-RPM Meter. ....................................................................... 172 Figure 118 National Instruments Hi-Speed USB Carrier. ....................................... 172
  15. 15. Design and Development of a Hybrid UAV xiv | P a g e ME5308 – Major Group Project Figure 119 Turnigy 4000 mAh LiPO Battery (6s). .................................................. 172 Figure 120 PWM changing the angle of a dc motor [95]. ....................................... 173 Figure 121 Sample calibration curve for the test bench. ........................................ 174 Figure 122 Numeric Loading for EDF and trend line. ............................................. 177 Figure 123 Thrust Results for the EDF................................................................... 178 Figure 124 Thrust efficiency of two and three bladed propellers [96]. .................... 179 Figure 125 VTOL Motor test with different propellers............................................. 180 Figure 126 Current Draw of the motor for any given thrust. ................................... 181 Figure 127 Laser cutting the aft EDF bulkhead ...................................................... 187 Figure 128 Fuselage during initial Epoxy resin stage of construction (left), tilting Propeller mount (Right) .......................................................................................... 188 Figure 129 rear view of the front Bulkhead displaying the nose gear mechanism.. 189 Figure 130 drilling axle holes on the non-vertical mounting plate of the carbon fiber Landing gear .......................................................................................................... 191 Figure 131 Rear landing gear assembly................................................................. 192 Figure 132 Fuselage structure with back-up rear undercarriage (left), Nose gear (right)...................................................................................................................... 192 Figure 133: Schematic of assembly of the aluminum VTOL motor mounts............ 193 Figure 134: Load tests conducted on the P400 ABS plastic (left) and the 3mm (right) plywood motor mounts. .......................................................................................... 196 Figure 135 EDF Mount to the fuselage, Side view (left), top view (right)................ 197 Figure 136 Reinforced rear landing gear mount..................................................... 203 Figure 137 Strengthened Retro-fit Nose Landing Gear.......................................... 204 Figure 138 Second flight test ground roll demonstration ........................................ 205 Figure 139 Second flight test tip stall demonstration.............................................. 206 Figure 140 Second flight test landing stall demonstration ...................................... 207 Figure 141 UAV in Tri-copter mode........................................................................ 209 Figure 142 V-n Diagram and Gust Loading graph.................................................. 211 Figure 144 Roskam Constraint Analysis ................................................................ 228 Figure 145 To obtain for Step 4 in Table 17 [49]....................................... 231 Figure 146 To obtain for Step 5 in Table 17 [49].................................. 231
  16. 16. Design and Development of a Hybrid UAV xv | P a g e ME5308 – Major Group Project List of Tables Table 1: Sketch of concept design idea.................................................................... 16 Table 2: Key parameters of individual concept design ............................................. 17 Table 3 Key parameters of individual proposal ........................................................ 18 Table 4 Individual proposal by Bennie Mwiinga ....................................................... 20 Table 5 Individual Concept Design........................................................................... 28 Table 6 Individual Concept #4.................................................................................. 31 Table 7 Typical Aircraft Parameters. [26] ................................................................. 33 Table 8 House of Quality table, How’s vs How’s ...................................................... 36 Table 9 Group Concepts .......................................................................................... 38 Table 10 Constraint Analysis Equations, obtained from Mattingly et All [27]............ 45 Table 11 Constraint Analysis Parameters. ............................................................... 46 Table 12 Different Wing Geometry Design Aspects ................................................. 49 Table 13 Wing Geometry Parameters...................................................................... 50 Table 14: Effects of changes in tail volume coefficients ........................................... 61 Table 15 Drag Components of the aircraft for cruise, 22.2 m/s. ............................... 69 Table 16: Time to achieve specific bank angles...................................................... 71 Table 17 Process to attain the lift curve slopes of the wing and the deflected control surface. ..................................................................................................................... 75 Table 18 Parameters and Results............................................................................ 76 Table 19 Lift variation with control surface deflection............................................... 77 Table 20: Horizontal and vertical tail design details.................................................. 82 Table 21: Static and dynamic stability requirements. [40] ........................................ 83 Table 22: Methods of determining the location of neutral point [38] [53] .................. 85 Table 23: Control Surface Functions........................................................................ 89 Table 24: Rudder deflection required during various landing at various crosswind velocities. ................................................................................................................. 95 Table 25 Rudder and elevator curve slope results using ESDU method, to be used in the control surface sizing.......................................................................................... 96 Table 26 showing properties of similar thickness plywood material strength [72] .. 125 Table 27 properties comparison of foam core wing reinforced with carbon fibre spars to balsawood ribbed structure reinforced with carbon fibre spars [77] ................... 128 Table 28 Battery properties for a suitable range of products [86]........................... 146
  17. 17. Design and Development of a Hybrid UAV xvi | P a g e ME5308 – Major Group Project Table 29 VTOL and STOL endurance.................................................................... 149 Table 30 Necessary Avionics Components for the UAV. ....................................... 151 Table 31 APM Anatomy Glossary. ......................................................................... 157 Table 32: Results obtained from the stress test conducted on the 3D printed component. ............................................................................................................ 168 Table 33 Testing Procedure for Motor Test............................................................ 176 Table 34 List of Suppliers and any comments surrounding orders and components delivered................................................................................................................. 183 Table 35 Mid-Project Budget.................................................................................. 212 Table 36 Final-Project Budget................................................................................ 213 Table 37 Wing profile: Additional Analysis ............................................................. 229 Table 38 VLM and Panel Method Result comparison from XFLR5 ........................ 230 Table 39 STOL Mission profile and current specifications...................................... 232 Table 40 VTOL Mission profile and current specifications...................................... 232
  18. 18. Design and Development of a Hybrid UAV xvii | P a g e ME5308 – Major Group Project Nomenclature  VTOL - Vertical Take-Off and Landing  STOL - Standard Take-off and Landing  EDF - Electronic Ducted Fan  MAC - Mean Aerodynamic Chord  CAD Computer Aided Design  AR - Aspect Ratio  Reynolds Number  - Weight Force  - Mass  - Air density  - Aspect Ratio of Horizontal Tail  - Volume Coefficient of horizontal tail  - Volume Coefficient of Vertical tail  - Area of Horizontal Tail  - Area of Vertical Tail  - Optimum arm of the Horizontal Tail  - Optimum arm of the Vertical Tail  - Area of Wing  - Centre of Gravity  - Static longitudinal stability  - Dynamic longitudinal stability  - Static directional stability  - Dynamic directional stability  - Location of Neutral Point  - Location of Centre of Gravity  - Location of Aerodynamic Centre  - Static Margin  - Efficiency of stabiliser  - Wing Curve Slope  - Horizontal tail Curve Slope  - Vertical tail Curve Slope  - Aircraft static longitudinal Stability Derivative  - elevator effectiveness directive  – control surface chord effectiveness parameter  - Wing Root Chord  - Wing Tip Chord  - Inboard location of ailerons  - Outboard location of ailerons  - Aileron deflection  - Aircraft rolling moment coefficient  - Approach Velocity  - Rolling Moment  - Steady state roll rate  - Wing Area
  19. 19. Design and Development of a Hybrid UAV xviii | P a g e ME5308 – Major Group Project  - Horizontal Tail Area  - Vertical Tail Area  Se - Elevator Area  ce – Elevator Chord  be - Elevator Span  – Induced Drag  - Bank Angle  - Second moment of area  ̇ - Steady State Roll Rate  - Lift at Take-off  - Rotational Velocity  - Moments about the aerodynamic centre  - Horizontal tail curve slope  - Aircraft Lift coefficient at take-off  - Maximum profile lift coefficient.  – Wing angle of attack  - Angle of attack  - downwash angle  - Horizontal tail incidence angle  - Angle of attack horizontal tail  - Elevator chord effectiveness parameter  - Elevator deflection  - Elevator effectiveness derivative  - Elevator effectiveness derivative  - Elevator effectiveness derivative  - Static longitudinal stability derivative  - Distance between aerodynamic centre and main landing gear  - Distance between centre of gravity and main landing gear  -Curve slope of wing-fuselage combination  - Vertical distance between thrust provider and centre of gravity  - Lift coefficient at cruise incidence angle  - Lift coefficient at zero wing incidence angle  - Crosswind velocity  - Aircraft side force due to crosswind  - Sideslip angle  - aircraft sideslip derivative  - aircraft sideslip derivative  - Vertical tail lift curve slope  - Aircraft control derivative  - Efficiency of vertical tail  - Vertical tail side wash gradient  - Rudder deflection  - Aircraft crab angle during crosswind landing  - Centre of aircraft side projected area  - Aircraft centre of gravity  - Aerofoil training edge angle
  20. 20. Design and Development of a Hybrid UAV xix | P a g e ME5308 – Major Group Project  - Slope of lift-coefficient curve with incidence for two-dimensional aerofoil in incompressible flow  - Theoretical slope of lift-coefficient curve with incidence for two- dimensional aerofoil in inviscid, incompressible flow  - Slope of lift-coefficient curve with control deflection for two- dimensional aerofoil in incompressible flow  - Theoretical slope of lift-coefficient curve with control deflection for two-dimensional aerofoil in inviscid, incompressible flow
  21. 21. Design and Development of a Hybrid UAV Arturs D. 1 | P a g e ME5308 – Major Group Project 1. Introduction 1.1. Motivation The UAV industry is developing rapidly and currently is a very popular topic due to the broad variety of applications of this technology. This increase in popularity creates higher demands in the field and calls for constant technological advance. There have been a number of projects which have involved designing, building and programming of unmanned aerial, some of these types of projects concentrated on developing autonomous flight and obstacle avoidance techniques. Usually such projects concentrate on one aspect since it is very time consuming especially as a university project where time is very limited and not all of it be dedicated to a project. Combining few of such aspect together is a lot harder and challenging due to time limitations and limited resources. Airports and aircraft carriers take up a lot of space due to lengthy runways which, creates some problems finding the airfields launching aircrafts even for home built RC planes. On the other hand, fixed wing aircrafts are very efficient for distance travelling and staying in the air longer comparing to rotor crafts. After individual concept designs have been proposed, the group selected a collaborated idea and it was decided to design, build and program a hybridised UAV of VTOL aircraft and fixed wing aircraft. This idea combines both concepts and enables using the benefits of both. After further research into hybrid UAVs, the decision was to develop a combination of tri-copter with fixed wing aircraft. At the time there was a quad-copter hybridised with a fixed wing aircraft however, a tri-copter has not been done before. Quad-copter combined with a fixed wing aircraft has at least 5 thrust generators unless it is a tilt rotor where, tri-copter has one less motor which can decrease overall weight of the vehicle. Such design could be developed further to improve specifications and achieve better performance and parameters than the existing UAVs on the market. A project like this have not been done at Brunel University previously therefore, success of this project would be a great achievement for the university and could even attract publicity and improve university rating.
  22. 22. Design and Development of a Hybrid UAV Arturs D. 2 | P a g e ME5308 – Major Group Project The project’s success could give a big contribution to university’s teaching curriculum regarding UAVs and improve it for future students. Due to tight time constraints of this project there will be a lot of room for improvement of this project, further development and expansion therefore, this project could be used as a dissertation topic for future years for individuals as well as groups. Once the UAV is fully ready it could be used as a learning platform for students about UAVs. At last, a project like this is a great way to apply the knowledge gained through 4 years of university where theory is applied to a real life problem to which the solution is yet to be found. Not only it is a way to apply the knowledge but also, there is a lot to be learned during the course of the project, aspects which have not been covered during the course of education. Besides the application of theoretical knowledge it allows to compare the theoretical input to outcome of the result and feasibility of theory in practice. Most important such project would allow each group member to carry out self-assessment and evaluate what they have achieved over the 4 year period of the course.
  23. 23. Design and Development of a Hybrid UAV Arturs D. 3 | P a g e ME5308 – Major Group Project 1.2. Project Description Initially the project idea was to design and build a UAV however, each group member had a different idea and view of the project. After proposing individual concepts, a combined idea based on individual inputs of the group members was carried forward, to design a fixed wing aircraft with short take-off/landing (STOL) ability as well as a vertical take-off/landing (VTOL) capability. Further decisions were made to design an electrical vehicle rather than using gas/fuel due to health and safety regulations and limiting time constraints. The fixed wing part of the aircraft is straight forward, conventional concept which have been used for almost a century now however, for VTOL is there were few considerations such as the number of rotors and their configuration. The optimum tri-copter configuration was selected to decrease the stability complexity. Also, tilt rotor configuration was excluded due to its increased complexity with additional servos and mechanics for tilt mechanisms. So the final decided concept design was of a fixed wing aircraft with one thrust generator for horizontal flight combined with 3 vertical motors (tri-copter configuration) for VTOL. The final, fully developed aircraft was planned to have the option of programmable, fully autonomous flight which does not need external, manual inputs to operate as well as a remote control capabilities. The aircraft required to be equipped with a camera allowing live streamed video to the user for surveillance purposes. However, due to very limited time constraints of this project, the realistic objectives had to be decided which involved designing and building the aircraft with functioning tri-copter configuration as well as the fixed wing, horizontal flight configuration. The aircraft had to be remote controllable for both configurations. If the main objectives are achieve, the secondary, optional objectives such as transition segment between VTOL and horizontal flight can be worked on. If the main objectives are achieved the project would be considered successful.
  24. 24. Design and Development of a Hybrid UAV Bennie M. 4 | P a g e ME5308 – Major Group Project 2. Literature Review 2.1. State of The Art Technology The idea of an aerial vehicle that can perform both VTOL like a helicopter as well as STOL like a fixed wing aircraft is not a new one. However limitations in technology as well as the complexity of the associated control system has prevented widespread development of these types of vehicles especially those with an autonomous nature. Recently a handful of fully autonomous hybrids have been unveiled some are still prototypes while others are fully functioning production models. Below are some examples of these state of the art V/STOL aircraft. Being able to hybridize rotorcraft and fixed wing aircraft provides the opportunity for further applications of UAV/S in roles that would normally be exclusive to either one or the other. The mini panther is a smaller version of its larger relative ‘The Panther’ and weighs 12 kg (shown in figure 1). It is however the newest Iteration in the family to date. It has 3 propeller motors, the front two motors tilt upwards. In conjunction with the aft propeller; that is permanently in the normal position relative to the aircraft, the mini- panther is able to perform vertical take-off and transition into cruise, as well as transition from cruise to stable hover flight. The third motor on the aft section of the fuselage acts as the third arm of a tri-copter when the front two are tilted, this allows for yaw control in hover and vertical flight. Figure 1 The IAI Mini Panther in level cruise flight [1] . Another approach to producing a VTOL aircraft is the V-Bat from MLB (shown in figure 2). It is an alternate solution to a VTOL UAV as it is designed as a sitter type aircraft. As a sitter type aircraft the V-bat begins its flight in a vertical position on the ground and then hovers to a predetermined altitude [2]. At said altitude it is able to
  25. 25. Design and Development of a Hybrid UAV Bennie M. 5 | P a g e ME5308 – Major Group Project transition autonomously from hover to cruise and vice versa. Developed with funding from DARPA, the military version also includes a 6 foot extending arm to pick up objects whilst at hover close to ground level [3]. This UAV is capable of flight up to 15,000 feet altitude, with a maximum endurance of 10 hours. Figure 2 Sitter type UAV the V-Bat from MLB [4]. Similar to the MLB V-Bat are systems that only use a ducted body design (Figure 3). These systems are sitter-type VTOL that also have a number of rotors (normally 4) placed in an X or + formation similar to a quad rotor. The rotors and control surface are all enclosed within a duct body. These duct type UAV are able to transition from hover to horizontal flight by tilting themselves forward and increasing and vectoring the thrust generated by one motor. An example of this design is the Santos Lab Orbis which currently uses a hydrogen fuel cell and has a span of 3.8m [5]. Figure 3 The Orbis from Santos Labs in hover [6] It is well known that rotor craft are able to perform VTOL in the most efficient manner. By hybridizing a rotor craft with a fixed wing craft the benefits of both types of vehicles can be maintained. Latitude Engineering, a small drone company from
  26. 26. Design and Development of a Hybrid UAV Bennie M. 6 | P a g e ME5308 – Major Group Project Tucson, Arizona USA has developed such a hybrid [7]. Calling it the Hybrid Quad rotor (HQ) (shown in Figure 4 below) it is simply a hybrid between a quad rotor and a fixed wing aircraft. It weighs 27 Kg and has 4 electric motors that it uses to hover and 1 gas powered motor mounted on the aft of the aircraft to provide thrust for forward flight. The HQ is still in development but Latitude Engineering has been able to maintain a hover and transition to forward flight. Figure 4 The Latitude Engineering HQ hybrid Prototype [8]. Another project that has taken the same approach as Latitude Engineering is the Wing copter V13CH project by Jonathan Hesselbarth. The Wing copter (shown in Figure 5) also hybridizes a fixed wing and a quad rotor, however, the Wing copter utilizes its 4 electric brushless motors to produce thrust in forward flight and in VTOL. Utilizing a set of swivel arms; on which the four motors are mounted, the Wing copter is able to perform transition from hover to horizontal forward flight and vice versa. This a novel solution that also requires a control system that can keep the aircraft stable while transition is being performed. The transition performed by the Wingcopter however not an automated one is and is instead manually controlled (with some assistance from on board flight control). By utilizing the rotary heads on a radio control transmitter, the controller is able to vary the tilt of the four motors and transition into horizontal flight.
  27. 27. Design and Development of a Hybrid UAV Bennie M. 7 | P a g e ME5308 – Major Group Project Figure 5 The Wingcopter V13CH in VTOL mode. Similarly employing a tilting mechanism to achieve VTOL is the Hammerhead developed by David Howe & Lyndon Caine of Advanced VTOL Technologies [9] (shown in Figure 6). It has a canard that helps improve the UAVs stall characteristics as well as the ability to thrust vector in order to limit pitch divergence [9].The hammerhead employs twin counter rotating electric rotors stationed on a tilting stub wing assembly which AVT claims “minimises pitch, roll and yaw coupling” [9]. The hammerhead is capable of performing either STOL or VTOL. In STOL mode the tilt wing stub is positioned such that the rotors produce a thrust propelling the UAV forward. In VTOL mode the tilt wing stub is positioned vertically allowing the hammerhead to take off and hover like a helicopter. Figure 6 Advanced VTOL Technologies' Hammerhead [10] Another example of hybrid VTOL design is the Bell Eagle Eye UAV (see Figure 7). Developed by Bell Helicopter – Textron, Texas USA. It is a Tilt rotor UAV capable of VTOL which it achieves by tilting its nacelles in the appropriate direction to either perform VTOL or STOL. The Bell Eagle Eye has a payload weight of 90kg, a maximum speed of 200kt and an endurance of 8 hours [11] [12]. It also utilizes an automated flight control system to assist in performing transition.
  28. 28. Design and Development of a Hybrid UAV Bennie M. 8 | P a g e ME5308 – Major Group Project Figure 7 Bell Eagle Eye Tiltrotor UAV [11]. Use of tilting mechanisms can also be found in other hybrid VTOL aircraft such as the QTW-UAV by Chiba University, Japan (see Figure 8). The QTW-UAV uses 4 rotors placed on tilting wings that swivel to the vertical position to gain altitude and then swivel forward to transition to horizontal flight. It utilizes 4 electric rotors giving it a payload weight of 5kg, endurance of 15 min and a max speed of 81kt [13]. Figure 8 QTW-UAV developed by Chiba University, Japan [14].
  29. 29. Design and Development of a Hybrid UAV Camilo V. 9 | P a g e ME5308 – Major Group Project 2.2. Market Analysis In order to design a vehicle fit for purpose, market research was undertaken to find a suitable starting point to work to. Typical dimensions and functionalities of existing real world UAVs were used to compare the sizes the aircraft under development should be close to. Below is a diagram showing a triangular relationship between wing span, total length, and Max Take-off weight with a logarithmic scale. Figure 9 Graph showing basic relation between small UAVs AV RQ 11 B Raven [15] Bayraktar Mini UAS [16]
  30. 30. Design and Development of a Hybrid UAV Camilo V. 10 | P a g e ME5308 – Major Group Project AV Wasp III [17] Innocon Micro Falcon [18] The graph on Figure 9 Graph showing basic relation between small UAVs represents information gathered on similar sized small UAV platforms. This was used during the early stages of initial geometric sizing to ensure the values that were being calculated for the aircraft were within a set industry trend. In essence it was an early rudimentary matching plot to define design tendencies for wingspan, vehicle length, and Maximum Take-Off weight. Both the first converged group concept as well as the current project aircraft design are listed on the plot. An important performance parameter to note is that the cruise velocities were not included in analysis as values could not be found for all vehicles looked at. However when averaged out along other smaller UAVs, typical cruise velocities were around 20 . Once the vehicle size had been constricted to a hypothetical box, performance characteristics were then researched for a broad range of UAVs. Figure 10below was sourced out from a thesis from MIT, displaying the relationship between Maximum take-off weight and endurance in hours for a wide variety of UAVs. The theoretical project aircraft would lie between 1 kg to 10 Kg along the bottom axis. This range on the plot has a trend of a maximum endurance of 1-2 hours. Considering the vehicle in question would be a hybrid, the added dead weights, the use of all-electronic propulsion as well as a vertical flight mission segment which would drain a higher amount than the usual battery draw during straight level un- accelerated flight would all impact this maximum endurance value. As a result it would be expected to be significantly lower in reality.
  31. 31. Design and Development of a Hybrid UAV Camilo V. 11 | P a g e ME5308 – Major Group Project Figure 10 Maximum Endurance vs. Maximum Take-off weight for a range of UAVs [19] This market research of current UAVs in service was invaluable in producing information to use as a guideline to the aircraft design process. After every main phase was completed values of the aircrafts performance, and sizing was checked with current vehicles such as these. From this initial selection of fixed wing UAVs, the variety was narrowed down to include specialized aircraft which were applicable to similar mission profiles, which is to say a fixed wing UAV that has VTOL functionality.
  32. 32. Design and Development of a Hybrid UAV Abbinaya T.J. 12 | P a g e ME5308 – Major Group Project 3. Requirements 3.1. Regulations Every country has its own aviation regulations. The Civil Aviation (CAA) Authority states that any UAV exceeding a weight of 7 kg need to be certified or approved. Due to this, the main priority of the aircraft was its weight. It was decided that the aircraft’s maximum take-off weight was kept under 6.5 kg and this was ensured throughout the design process. However, the CAP 722 and CAP 393 Air Navigation Order states that aircraft that weigh less than 7 kg should also follow some regulations depending on whether they are being used for commercial purposes or not. The regulations for aircraft with a mass of less than 7 kg states that the aircraft should abide by appropriate operational constraints in order to ensure public safety. The regulations are based on the flying operation being conducted and the potential risks to any third party. General principles for UAV operations outside segregated airspace should follow an approved “detect and avoid” system and avoid crowded areas. It is also important for the aircraft to not fly beyond the visual line of sight. The CAP 722 also states that the aircraft should be flown such that the pilot controlling it can take manual control at any point of time and fly the aircraft out of danger. It also states that the aircraft should not be flown above 400 feet at any point of time. Further details of regulations applicable to this UAV can be found in the CAP 722 and CAP 393 of the Civil Aviation Authority Air Navigation Order. These regulations were kept in mind throughout the build of this UAV. [20] [21]
  33. 33. Design and Development of a Hybrid UAV Arturs D. 13 | P a g e ME5308 – Major Group Project 3.2. Aims and Objectives Aim To design, manufacture and test an aircraft of fixed wing configuration hybridised with a tri-copter. Horizontal flight capabilities of the aircraft have to be demonstrated as well as the VTOL capability using a remote control transmitter. . Objectives 1. To use aircraft design techniques and approaches to design a fixed wing tri- copter hybrid aircraft 2. To test and prove the suitability of load critical components of the aircraft 3. To build and test the final selected UAV design 4. To program the aircraft and have the avionics ready for both horizontal and vertical flight 5. Carry out a demonstrative flight for each of the configurations of the UAV
  34. 34. Design and Development of a Hybrid UAV Abbinaya T.J. 14 | P a g e ME5308 – Major Group Project 3.3. Mission Profile The purpose of the UAV is to be able to perform a surveillance and reconnaissance role. This requires the aircraft to be equipped with a camera and live stream capabilities. The main concept of this project is to design an aircraft that is capable of a Vertical Take-off & Landing as well as a Short take-off and landing (V/STOL). This would allow for the UAV to be launched from different environments where a runway is not available such as urban areas with limited airspace or launches from the sea. Due to the tight time schedule and the complexity of the project the transition between vertical and horizontal flight is not a priority for the project. Initially the UAV has to be able to perform a VTOL mission: take off vertically, climb, hover, climb further, hover at new altitude and descend to land. For the STOL mission it has to perform a separate mission profile where the aircraft has to: take-off, climb, cruise, loiter, descend and land. It is expected that parts of the mission profile segments are performed autonomously by an on-board autopilot. Figure 11 and 12 below illustrate the mission profiles allocated for the STOL and VTOL flight. The calculations of the mission profiles were done based on the current drawn from the batteries to be used. The total time of UAV operation for the STOL mission should be at least 9 minutes. The UAV should be able to operate for around 3 minutes when performing the VTOL mission. Figure 11: The STOL mission profile. 0 5 10 15 20 25 30 35 0 100 200 300 400 500 600 Altitude(m) Time (s) STOL mission profile
  35. 35. Design and Development of a Hybrid UAV Abbinaya T.J. 15 | P a g e ME5308 – Major Group Project Figure 12: The VTOL mission profile. Even though the transition is not a set priority for the project at the moment, it is most likely to be attempted once the VTOL and STOL missions have been successfully completed. In the case of the transition being attempted, the aircraft should be able to operate for around 4 minutes. In order to design and develop the UAV an appropriate design procedure must be performed. Since the project is aerospace orientated, the avionics and electronics to be used by the UAV are to be off-the-shelf components that are marginally modified to assist in the completion of the project objectives. The aircraft should be safe to operate, undergo a safety assessment and meet minimum requirements for this type of aircraft. The UAV is to be equipped with a flight control system capable of autonomous flight and manoeuvres. However, for the purposes of build and testing the UAV will be remotely controlled by a human pilot via a radio receiver and transmitter controller. 0 2 4 6 8 10 12 14 16 0 10 20 30 40 50 60 70 80 90 Altitude(m) Time (s) VTOL mission profile
  36. 36. Design and Development of a Hybrid UAV Abbinaya T.J. 16 | P a g e ME5308 – Major Group Project 4. Design Process 4.1. Concept Design 4.1.1. Individual Proposals Abbinaya T Jagannathan Table 1: Sketch of concept design idea The aim of this design concept is to have an autonomous UAV that is suitable for reconnaissance and surveillance purposes. The objective of this UAV design was to have an aircraft that is aerodynamically sound and also attempt to achieve a vertical/short take-off or landing. A push propeller was to be used at the fuselage to provide the main forward thrust. The integrated motors at the wing are meant to provide vertical thrust. Since the design consists of only 2 vertical thrust providers, the feasibility of VTOL is uncertain and if this is the case then, the goal is to achieve a short take-off by using the vertical thrust providers. The fuselage in this design is shaped as an aerofoil to have a body that is able to contribute to the lift force produced by the aircraft. An aerofoil with a high thickness to chord ratio is to be used for the fuselage. The figure above illustrates an idea of the UAV proposal. From the figure it can be seen that the other key aspects of this concept are the V-tail and the use of winglets. The V-tail was selected mainly because of the push propeller to be used at the rear end of the fuselage. Other reasons for V-tail selection are that it has a smaller size therefore; it will be lighter
  37. 37. Design and Development of a Hybrid UAV Abbinaya T.J. 17 | P a g e ME5308 – Major Group Project and have a smaller wetted area which would result in drag reduction. The V-tail configuration also uses fewer control surfaces compared to a conventional tail. These control surfaces are called ruddervators and are a combination of rudder and elevators. [22] The use of winglets was also considered in the concept for a number of reasons. Winglets are small wing-like lifting surfaces that are fitted at the tip of the wings for the purpose of reducing the trailing-vortex drag. As a result, this would increase the lift generated on the aircraft. [23] The materials considered for this design were a combination of foam and carbon composites (main airframe) which are both lightweight materials that can take high loads. Category Abbinaya T Jagannathan Mission Type Reconnaissance/ Surveillance Environment Outdoor Design Type Modular Modular Options Camera TO (Take-Off Type) V/STOL L (Landing) V/STOL Powerplant 1× Push Propeller & 2 × Rotor Integrated in Wings Wing Medium/High Fixed Wing Tail V-Tail Airframe Foam & Carbon Composite Landing Gear Fixed Endurance(Prospective) 60 min Altitude 50-100 m Glide Capability (Inc. Design) Yes Radio Controlled Back up Yes Autonomous Yes Table 2: Key parameters of individual concept design
  38. 38. Design and Development of a Hybrid UAV Arturs D. 18 | P a g e ME5308 – Major Group Project Arturs Dubovojs Figure 13 approximate sketch of the concept idea Category Arturs Dubovojs Mission Type Reconnaissance/ Payload delivery Environment Outdoor Design Type Modular Modular Options Cargo/Camera Take-Off Type Catapult Landing Parachute/STOL Power plant 1x Push Motor Wing High Fixed Wing/Joint Wing Tail Conventional/ Tailless (Joint Wing) Airframe Foam Landing Gear Fixed Endurance (Prospective) 2 hours Altitude 100m Glide Capability (Inc. Design) Yes Radio Controlled Back up Yes Autonomous Yes Table 3 Key parameters of individual proposal Initial idea was to Design and build a high endurance UAV with recon and payload delivery capabilities for outdoor use. The aircraft had to be able to carry a live
  39. 39. Design and Development of a Hybrid UAV Arturs D. 19 | P a g e ME5308 – Major Group Project streaming camera and a small payload. It has to be designed to be able to take off and land in a standard manner as well as been optimised for catapult mechanism and a parachute for emergency, vertical landing. Take-off and landing would require a landing gear, for weight reduction and less complexity a fixed landing gear would have been used. Aircraft required being equipped with only one push/pull propeller either on the nose or top of the fuselage with an electric motor capable of providing enough thrust. The aircraft would have to be able to carry out autonomous flight as well as a radio controlled option. After the basic mission and guidelines been set an investigation into wing types was carried out. A joint wing configuration was selected for the aircraft because of its ease of implementing it to a small scale UAV in comparison to a full scale aircraft. Since the aircraft should have a catapult mechanism it should be relatively small and compact for ease of deploying in unequipped circumstances, joint wing configuration reduces the required wing span. Since the joint wing configuration is relatively new invention it has not been implemented on many full scale aircrafts and there is mainly research being carried out on using it on smaller scale, high altitude UAVs. The joints between the wings would act as winglets, reducing induced drag. The option of having a tail additionally to the joint wing was still available. A tail would improve the aircrafts manoeuvrability by adding yaw capability which joint wing aircrafts lack. Also by making a separate control surface – tail, the second wing would become a lifting surface therefore, would generate more lift.
  40. 40. Design and Development of a Hybrid UAV Bennie M. 20 | P a g e ME5308 – Major Group Project Bennie Mwiinga Bennie Mwiinga Mission Type Recon/Surveillance Environment Outdoor & Urban Design Type Modular Modular Options Camera TO (Take-Off Type) V/STOL L (Landing) V/STOL Power-plant 3x Ducted Fans Wing Mid Fixed Wing Tail H-Tail Airframe Carbon Composite/Foam Landing Gear Fixed Endurance(Prospective) 180 Mins Altitude 60+ m Glide Capability (Inc. Design) No Radio Controlled Back up Yes Autonomous Yes Table 4 Individual proposal by Bennie Mwiinga The current military and commercial applications of UAV/S has increased in the past 14 years at an exponential rate. Also the environments in which these systems are expected to operate have changed and outdoor operations require novel design solutions in order to accomplish requirements such as quick deployment, long range and endurance. Military operations are more frequently being carried out in urban environments where close quarter combat is conduct. The ability to have a UAV that can be used in such an environment would assist troops in such operations by being able to be deployed on the spot to conduct reconnaissance and surveillance. This proposal is shown in Figure 14.
  41. 41. Design and Development of a Hybrid UAV Bennie M. 21 | P a g e ME5308 – Major Group Project Figure 14 Individual Proposal Concept by Bennie Mwiinga. In order to achieve these requirements a V/STOL type system is proposed. V/STOL would allow for the UAV to be deployed in any terrain or environment without the requirement of having a prebuilt runway. The V/STOL system in this proposal is achieved by having two ducted fans mounted on the wing tips that are able to tilt for vertical and horizontal flight. This approach was taken by the Doak Aircraft Company in developing their Doak VZ-4 (Figure 15) in 1958. Figure 15 The Doak VZ-4 by Doak Aircraft Company [24]. An additional ducted fan is then placed on the aft of the aircraft to provide additional forward thrust for STOL and transition to horizontal flight. The use of ducted fans may seem to be the wrong choice due to the lower efficiency when compared to a purely fan based propulsion. As can be seen in equation 4 Area (A) if increased will increase the amount of force created. A prop or fan has the advantage that it can have a wide area and move more mass of air and thus create more force. A ducted fan however has a smaller area and to move the same amount of air as a prop or fan it has to increase the rate at which it accelerates the air while moving a smaller amount.
  42. 42. Design and Development of a Hybrid UAV Bennie M. 22 | P a g e ME5308 – Major Group Project (4.1.1.1b) Where (4.1.1.2b) ∴ (4.1.1.3b) Where (4.1.1.4b) (4.1.1.5b) At the time the Doak was engineered this statement would be true, however, modern day ducted fans (electric) are designed and engineered to operate at higher efficiencies as loses are reduced by designing more aerodynamic shrouds and utilizing more efficient electric motors. These new generation of ducted fans have been used by many entities ranging from RC Hobbyists to UAVs developed by companies like Honeywell and Boeing. These ducted fans utilise higher efficiency motors capable of high rpm and specially designed props to produce high level performance. A modular type design would be used in this proposal. It would also allow for the UAV to service other sectors such as agricultural monitoring and scientific research, as the UAV would be capable of being outfitted with varying types of payloads such as FLIR or other EVS.
  43. 43. Design and Development of a Hybrid UAV Brett M. 23 | P a g e ME5308 – Major Group Project Brett McMahon Figure 16 Blown Flight Control Concept This design is inspired to some extent by the DEMON concept demonstrator [25] developed by BAe Systems, Cranfield and other universities which used jets of air to control the aircraft in flight. Using low profile wing tip fans, the aircraft will be able to perform roll manoeuvres using pulses of air from the appropriate fan. Short take off performance would be possible using both fans together to provide lift in addition to that provided by the main wing. The aircraft would be propelled through the air using a large pushing motor of sufficient power (with reserve) to achieve a desired flight speed. The aircraft would be all electrically powered for relative simplicity and safety compared to petrol powered motors and their required ancillaries. Two batteries are In-wing motors, provide short take off and airbourne roll control Camera provides visual target ‘hit’ data Rod and slot construction method, removable wings if needed Internal components laid out with respect to a selected Centre of Gravity position Internal avionics components mounted on aluminium cruciform, outer surfaces of foam or vacuum formed plastic shell pieces Infra-red range finder provides altitude data to flight controller
  44. 44. Design and Development of a Hybrid UAV Brett M. 24 | P a g e ME5308 – Major Group Project envisaged for the aircraft, one large capacity battery used for the forward thrust provider and wing tip motors while a second smaller battery would independently supply the flight control systems. The primary potential benefits of the wing tip fan arrangement is the level of simplicity that can be achieved over the otherwise complex arrangements associated with moving flight control surfaces, whilst also allowing for some moderate weight savings. The wings will be designed so they can provide the lift required with minimal drag at moderate flight speeds. Sizing of the aircraft must be sufficient such that the body can adequately house all the avionic components as well as provide a small degree of flexibility for adjustments (moving or addition of components) which might be needed during refinement. The wings must be able to generate more than enough lift required to support the aircraft’s mass, with a margin of safety for gusting conditions or lack of performance from the propelling motor. The flight control system will most likely be based on the Ardupilot series of control boards available at many remote control hobby shops. The benefit of these control systems is their general availability, relatively cheap price and extensive programming support from the remote control operator community. Power distribution, relays, wiring and programming must be defined separately and accounted for in the budget to be defined later. Materials will be determined that possess sufficient strength for the specified application whilst having minimal weight. All materials must be readily available from local suppliers and be sourced at the lowest price possible. Construction techniques used must be such that the overall component weights are kept as low as possible. Processes and tools required for fabrication and assembly must be simple and readily available through the university workshops or specially bought in by ourselves. Total aircraft cost must not exceed departmental budget constraints to be discussed with the project supervisors. After discussions within the group, the main problem with this aircraft concept was the general lack of elevator and tail sections required for pitch and yaw control. Roll control is managed primarily by the wing motors but additional aileron control surfaces may need to be added for higher speed flight, to be determined as the design progressed.
  45. 45. Design and Development of a Hybrid UAV Brett M. 25 | P a g e ME5308 – Major Group Project Conceptual Fuselage Design The fuselage is the main body of the aircraft. Depending on the aircraft layout, the fuselage is responsible for housing fuel, weapon stores, cargo, avionics equipment and passengers. For the UAV aircraft, the fuselage will house all of the electronic parts such as the flight control boards, navigation systems, cameras and radio receivers as well as the batteries. In addition to housing of the internal parts, the fuselage must also provide the fixing structure for the aircraft’s other component parts such as the wings, motors and the landing gear. The fuselage concept shown below in Figure 17 uses a thin walled outer skin and a removable avionics tray, which slides along runners extending the full length of the fuselage. This approach has previously been used by remote control aircraft builders as shown by Figure 18. The avionics tray allows for very tight packaging of the internal electronics and batteries of the aircraft and would be fully removable for servicing and adjustment, save for a few connections to the aircraft control surfaces such as ailerons, elevators, rudder and the motors. Figure 17Tube and Tray Fuselage Concept
  46. 46. Design and Development of a Hybrid UAV Brett M. 26 | P a g e ME5308 – Major Group Project Figure 18 Tube and Tray Fuselage as Used by Hobby Flyers Dependant on material availability and price, the thin walled (approximately 0.5 to 1mm thick) fuselage material of plastic or aluminium would allow for the required strength and low weight but could be further reinforced with the addition of stringers running top and bottom of the fuselage (along with the metal runners for the avionics tray located along the mid-line). This simple construction with easy access via the tray arrangement could be made almost entirely from off the shelf parts and materials. The wing box junction would have to be specially made to encompass the mid wing section. This junction would then be mated to the fuselage tubular section using fore and aft fastening wedges. Screws would be inserted through the fuselage skin and into the wedges, holding it (and therefore the wing box section) firmly in place. Toward the nose of the aircraft, a swivelling fan arrangement would be fixed between two bulkheads allowing the fan to be adjusted using a dedicated servo mechanism to counteract unwanted yaw from the other lift fans when the aircraft is in vertical flight. Further ahead of the swivelling fan arrangement would be a clear plastic nose cone, inside which the video camera and GPS receiver could be mounted, providing a clear view ahead and upward. The nose section would likely be a two part assembly made from either specially ordered injection moulded acrylic or made on campus using a vacuum forming method. This concept however was not used for the final aircraft as the required plastic or metal thin walled, large diameter fuselage tubing could not be sourced at reasonable cost. A case was therefore made for a bespoke fuselage design which could be
  47. 47. Design and Development of a Hybrid UAV Brett M. 27 | P a g e ME5308 – Major Group Project tailored to the changing requirements as the design and the parts specification evolved.
  48. 48. Design and Development of a Hybrid UAV Camilo V. 28 | P a g e ME5308 – Major Group Project Camilo Vergara Category Camilo Mission Type Recon/Multi-role Environment Outdoor Design Type Modular Modular Options Cargo/Camera TO (Take-Off Type) V/STOL L (Landing) V/STOL Powerplant 2x Tilt EDF & 1x Fixed VTOL EDF Wing Mid/High Fixed Wing Tail Boom tail Airframe Metal/Foam Landing Gear Fixed Endurance(Prospective) 90-120 Mins Altitude 100m Glide Capability (Inc. Design) Powered Radio Controlled Back up Yes Autonomous Yes Table 5 Individual Concept Design Every UAV design incorporates various design solutions and ideas as well as a set level of autonomy that is dictated by its mission parameters and operating environment. For the purpose of exploring different approaches to the design problem presented, various types of configurations were looked at. The potential for a VTOL system on a fixed wing reconnaissance drone is significant. Not only would it eliminate the need for a runway and be easy to retrieve which essentially makes it deployable from any location, but from an intelligence aspect, it would be able to do what no other normal type of fixed wing UAV could do, which is stop and hover mid-air over a point of interest allowing for a detailed inspection of
  49. 49. Design and Development of a Hybrid UAV Camilo V. 29 | P a g e ME5308 – Major Group Project the area ahead instead of having to perform circuits or flyby’s around a target. In order to achieve this, a particular solution was researched. This initial VTOL system came in the form of a tilt rotor design, which has its origins from the V-22 Osprey. Upon First glance there seems to be a very select few UAV’s currently on the market with this type of technology, the biggest being the Bell 'Eagle eye' which was a true representative of the twin tilt rotor Osprey. There are a couple more variations to mention, the first being Israeli Aerospace Industries ‘Panther’ VTOL UAV utilizing a 3 motor design with 2 being mounted on the wings, and a third around the rear section of the fuselage. Another worth mentioning is a prototype VTOL aircraft called the ‘phantom swift’ by Boeing which incorporated 4 ducted fans, two being located at opposite wing tips, and two being incorporated into the fuselage itself. Below is a diagram of the initial concept inspired from existing real world solutions. Figure 19 Concept Sketch of an initial idea The challenge of such a design would include aspects like the complexity of the control system integrated into the autonomous nature of the UAV. From a design perspective, several considerations must be taken into account for an aircraft of this nature. with regard to the power-plants themselves, this would include the position of the rotors from the longitudinal center of gravity, the connections between the servos and motors themselves, the physical connections to the wing or fuselage depending on the motors location, and the individual propeller rotation direction. The power output of the motors utilized would be a design aspect, due to the extra weight of the
  50. 50. Design and Development of a Hybrid UAV Camilo V. 30 | P a g e ME5308 – Major Group Project control system for a tilt rotor design, the motors selected must have enough power to lift the aircraft vertically, as well as perform well at horizontal flight. Electronic Ducted Fan (EDF) systems have rarely been used for VTOL hybrid applications; so the aircraft would be experimental by nature.
  51. 51. Design and Development of a Hybrid UAV Carlos C.M. 31 | P a g e ME5308 – Major Group Project Carlos Calles Marin Category Carlos Mission Type Recon/Surveillance Environment Outdoor Design Type Modular Modular Options Cargo/Camera TO (Take-Off Type) STOL L (Landing) STOL Power plant 1x Push Motor Wing High Fixed Wing Tail Boom Tail Airframe Balsawood Landing Gear Fixed Endurance(Prospective) 60 min Altitude 100 m Glide Capability (Inc. Design) Yes Radio Controlled Back up Yes Autonomous Yes Table 6 Individual Concept #4 The initial idea for the concept was very conservative. The initial requirements for the design were “very short landing and take-off or hand launched” and some aspect of autonomous behaviour. From the design point of view these are the different configurations considered: 1. Type of wing – High, Medium or Low 2. Power plant – Tractor, Pusher or both 3. Tail Type – V-Tail, Standard or Boom Tail 4. Wing – Sweep, Taper, Dihedral, Wash-in/out A high wing was chosen because the aircraft had to be possibly hand launched, which means that it needs good stability at low speeds until it reaches cruise. High mounted wings have better lateral stability than medium or low mounted. Considering the power plant the pusher configuration was chosen to improve the aerodynamic performance. The flow behind the propeller no longer has to flow over the wings, which would be the case with a normal tractor power plant. There are some situations were both types are used in to increase the thrust provided, acting in
  52. 52. Design and Development of a Hybrid UAV Carlos C.M. 32 | P a g e ME5308 – Major Group Project line with the centre of gravity. In this case it would not be necessary to have so much thrust. Regarding the type of tail needed V-Tail was quite interesting, reducing the amount of drag produced by the tail. For the pusher propeller configuration chosen a Boom- Tail is required to correctly place the motor. This doesn’t discard the V tail, but it changes it into inverted V. the problem with V tail is that it requires more expert knowledge of coding to have autonomous behaviour. The standard Boom Tail was chosen to avoid any control problems. In terms of wing design, sweep would not be an option because it is intended for high speed flight and this aircraft would fly at relatively small speeds. Taper would increment our performance, by reducing wing tip vortex downwash effect. The optimal wing shape would be elliptical to have a uniform span wise distribution of lift with the lowest induced drag possible. Due to its hard manufacturing process the elliptical wing shape can be approximated by a straight tapered wing, with a taper ratio of 0.3-0.4, hence it would be desirable to have a taper ratio around those values. The drawback of uniform lift distribution is that stall is reached evenly throughout the wing plan form; therefore washout would have to be considered to have more margin for error. Dihedral would increase the stability, but decrease the effective span of the aircraft, therefore it is not going not be part of the concept. To control the aircraft autonomously some readily available micro processing computers were thought of. There are two options which are Arduino and Raspberry Pi, these are open source platforms with widely available codes that can perform as an autopilot for the aircraft. Figure 20 is a representation of the initial concept where the taper, boom tail and pusher propeller can be observed.
  53. 53. Design and Development of a Hybrid UAV Carlos C.M. 33 | P a g e ME5308 – Major Group Project Figure 20 Concept Design Sketch. To achieve good aerodynamic performance and the main mission aim, short take off/landing, the concept to should have a similar look to that of a glider with high aspect ratio, minimal weight and streamlined. RC trainer aircraft were also taken into consideration since they are supposed to be easy to handle, which would benefit the autonomous nature of the aircraft. Table 7 shows typical design aspects for a trainer aircraft: Trainer Aircraft Glider Wingspan (b) 152 cm 152 cm AR 6-7 8-10 Overall Length 127 cm 102 cm Wing Area (S) 0.4216 m2 0.323 m2 Flying Weight 1.81 Kg 0.454 Kg Wing Loading (W/S) 59 N/m2 20 N/m2 Table 7 Typical Aircraft Parameters. [26]
  54. 54. Design and Development of a Hybrid UAV Carlos C.M. 34 | P a g e ME5308 – Major Group Project To have an idea of what speeds the aircraft would be flying at an initial estimate of the weights was made as a group effort, and came to the conclusion that the aircraft would weight about 3.7 Kg. √ It can be shown that the aircraft would need a velocity ( ) of with a wing area ( ) of to fly. Using the Aspect Ratio formula the span can be determined. √ The wingspan comes to be around .
  55. 55. Design and Development of a Hybrid UAV Arturs D. 35 | P a g e ME5308 – Major Group Project 4.1.2. Quality Function Deployment Figure 21 A quality function deployment (QFD) Matrix Figure 21 demonstrates House of Quality, How’s vs How’s which demonstrates the importance of different parameters in terms of percentage as well as the importance in relation to other parameters. Main two parameters were determined to be the Electrical efficiency and Hover Capability. Hover capability if one of the main objectives of the project therefore it is one of the main parameter on the other hand if the system is not efficient enough the current will be drawn very rapidly during hover mode since there are 3 motors that would be operating at the same time therefore, it is essential for the electrical system to be efficient otherwise there would not be enough electrical power to fulfil the mission profile. The third most important parameter for Table 8 is the overall weight of the aircraft for the same reason the previous one. The lower the weight of the aircraft the less current it draws, the less power required to operate it which leads to improve in efficiency. Those are three main aspects of the aircraft which were concentrated the most on during the design and the built phase of the project.
  56. 56. Design and Development of a Hybrid UAV Arturs D. 36 | P a g e ME5308 – Major Group Project Nevertheless, the other parameters of the aircraft are very important and failure to reCGnise that could lead to unsuccessful project. Aircraft Attribute Score Importance (%) Relative Importance (%) Electrical Efficiency 84.33 100.00 15.99 Hover Capability 71.00 84.19 13.46 Weight 65.67 77.87 12.45 Cruise Speed 41.67 49.41 7.90 Reliability 40.78 48.35 7.73 Range 38.78 45.98 7.35 Drag 37.44 44.40 7.10 Manufacturing Costs 29.44 34.91 5.58 Easy to operate 23.44 27.80 4.45 STOL Distance 23.00 27.27 4.36 Noise 22.11 26.22 4.19 Rate of Climb 17.67 20.95 3.35 Max g-loading 12.11 14.36 2.30 Maneuverability 8.56 10.14 1.62 High quality image 6.11 7.25 1.16 Operation beyond line of sight 5.22 6.19 0.99 Table 8 House of Quality table, How’s vs How’s
  57. 57. Design and Development of a Hybrid UAV Abbinaya T.J. 37 | P a g e ME5308 – Major Group Project 4.1.3. Group Concept Category Initial Group Concept Design Final Group Concept Design Mission Type Reconnaissance/ Surveillance Reconnaissance/ Surveillance Environment Outdoor Outdoor Design Type Modular Modular Modular Options Camera Camera Take-Off Type V/STOL V/STOL Landing V/STOL V/STOL Power plant 1x STOL EDF & 3x VTOL EDFs 1x STOL EDF & 3x VTOL Propeller Motors Wing High Fixed Wing High Fixed Wing Tail H-Tail Boom Tail Airframe Balsa Ply wood, Foam, Carbon Composites and Balsa Landing Gear Fixed Fixed Endurance (Prospective) 30 min 30 min (depending on motor thrust test) Altitude 40 - 60m 40 - 60m Glide Capability (Inc. Design) Yes Yes Radio Controlled Back up Yes Yes Autonomous Yes Yes
  58. 58. Design and Development of a Hybrid UAV Abbinaya T.J. 38 | P a g e ME5308 – Major Group Project Pictures Initial Group Concept Design Final Group Concept Design Table 9 Group Concepts
  59. 59. Design and Development of a Hybrid UAV Abbinaya T.J. 39 | P a g e ME5308 – Major Group Project Table 9 outlines the basic ideas of the group concept designs. After discussion and consideration of the various ideas proposed an initial group concept design was confirmed. The final concept design was evolved with changes being made to design in order to make initial design more feasible. When comparing the sketches of the initial group concept and the final group concept a lot of differences can be noticed. One such change made is the change in placement of the VTOL motors from the wing tips to the behind the wings. The VTOL motors were initially placed at the wing tips and then moved to be integrated into the wing. This change was made in order to reduce the loads on the wing tips as well as to reduce the moment arm that could possibly flutter and generate some moments on the wing. This change was also opted because it could possibly reduce the drag generated on the aircraft. However, this configuration of the VTOL motors being integrated in to the wing was again changed to be placed behind the wings just as in the current concept. This was done due to some stability issues that came up with the VTOL tricopter system. Another major change in concept design was made with material selection. Balsa was selected for the initial concept design as it is a traditional material used in small UAV and remote controlled planes. This changed when in depth research was conducted on various other materials. With the knowledge gained from research, the traditionally used balsa was replaced with other modern materials and composites. A lot of other changes with design had also been made to the aircraft before deciding on the final concept because of conflicting design issues between the systems required for the VTOL mission and the systems required for the STOL mission. Successful completion of the given design concept should provide an UAV that is capable of doing a vertical take-off and landing as well as a standard take-off and landing. The propulsion system available for VTOL is a tri-copter made of propeller motors. The tri-copter is designed such that there are two counter rotating motors behind each wing and one motor at the nose of the aircraft. The motor at the aircrafts nose would be equipped with a tilt mechanism in order to counteract the yaw force. The thrust for the normal flight would be provided by an Electric Ducted Fan (EDF). The EDF would be placed at the aft of the fuselage in order to provide push propulsion.
  60. 60. Design and Development of a Hybrid UAV Abbinaya T.J. 40 | P a g e ME5308 – Major Group Project Other aspects of the design such as the wing and tail are kept fairly simple with no dihedral, twist or sweep. A boom tail was selected mainly to keep it from interfering with the EDF placed at the aft of the fuselage. Even though the concept design had been decided an open minded was kept during the phase of the design and manufacture to cope with unanticipated problems that could arise.
  61. 61. Design and Development of a Hybrid UAV Carlos C.M. 41 | P a g e ME5308 – Major Group Project 4.2. Preliminary Design Once there is a concept idea, the project may move forward into the preliminary design phase. It consists of making the concept idea reality, all the requirements and limits are applied in the aircraft/copter design calculations to obtain a unique outcome to complete the objectives stated. The preliminary design was decomposed into smaller subsections, allowing different group member to focus on individual tasks and work more efficiently. These subsections, along with the rest of the project, may be seen in the workflow diagram below, Figure 22
  62. 62. Design and Development of a Hybrid UAV Carlos C.M. 42 | P a g e ME5308 – Major Group Project Figure 22 Flow Diagram showing Design Stages Requirement s Market Analysis Technology Concept Design Initial weight estimation Flight control and avionics Aerodynamics Wing Geometry Initial Tail Sizing Propulsion Initial Layout Initial Costing Preliminary Design Initail CG estimation Performance Check Wing Aerofoil Selection Final Wing Design Final Tail Sizing Control Surface Design Lift Curve for Control Surfaces Fuselage Design Landing Gear Optimal CG and NP Motor and Propeller Selection Stability and Control Frozen Design Preliminary Budget and Costs Detail Design and Build Structure Technology Implementation and Sourcing CAD Model Material and Equipment Logistics Experiments and Testing Final Design Configuration Fabrication and Assembly Proof of Concept Ground Testing Flight Test Performance and Results Design Optimisation Final Optimised Design

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